Scrolling charts, banners or tapes that are alternately wound back and forth between a pair of rollers are commonly used on chart recorders, advertising displays and other devices where information must be continuously or intermittently displayed. In order to assure a smooth regular winding of the scrolling band and avoid creases and folds in the displayed section of the band between supply and take-up rollers, the band must be kept taut. This can be achieved by careful synchronization if the roller movements through precise guiding mechanisms, or by using tensioning idle rollers as disclosed in U.S. Pat. No. 3,726,031 Singer.
When separate motors are used to drive the rollers the speeds of the motors must be carefully matched. The scrolling system driving mechanism of the prior art are often complex, using driving gear assemblies which tend to be noisy and subject to vibration. The complexity of the prior art mechanism results in substantial cost of parts and assembly labor.
The present invention results from a search for a simple, yet precise and inexpensive scrolling chart mechanism that can be used on relatively small and portable devices particularly suitable for face-to-face teaching and sales presentation, window displays, as well as entertaining and decorative home photographic displays.